A pinch valve generally differs from conventional valves in that, instead of having closing elements that interfere with a fluid flow, they apply pressure on a sleeve to prevent a flow. When in open position, no closing element is present within the sleeve and the flow is unimpeded by the presence of the valve. Pinch valves are frequently used in applications where solid or semi-solid material, such as powder, granules, pellets, fibers or similar material, flow within the sleeve. They may be used in soft applications, such as for example in waste water plants, or in heavy industrial applications.
Conventional mechanical pinch valves apply pressure using a movable closure bar at one point of a circumference of the sleeve, for example at the top of the circumference, flattening the sleeve towards a fixed bottom, thereby greatly deforming the sleeve. Some pinch valves use air pressure for flattening the sleeve. However, mechanically driven presses are almost always screw-driven in large part due to high forces needed to close pressurized sleeves and almost always require fully encased sleeves.
In any case, pinch valves are primarily screw driven and require an elastomer sleeve with a pinch location in the centerline of the sleeve for wear purposes. The screw-driven linear gearing significantly reduces the mechanical efficiency; and, therefore copious amounts of power are required. This significantly increases the cost of the actuator-valve combination. The presence of a screw-driven system also requires multiple turns to drive the closure bars together which can drastically effect closure times and can lead to safety concerns where fast shut-off is needed.
Therefore, there is a need for a pinch valve that meets requirements of a broad range of applications while providing ease of maintenance, reduce thrust required to close, fast maintenance, and less costly actuators.